Gas driers



July 9, 1963 G. H. MITCHELL GAS DRIERS Filed Dec. 5. 1 960 5 Sheets$heet1 Inventor LEONARD G. H. MITCHELL Attorney July9, 1963 L. G. H. MITCHELL3,096,972

GAS DRIERS Filed Dec. 5, 1960 5 Sheets-Sheet 2 In venzor LEONARD G. H.MITCHELL [WWW Attorney July 9, 1963 G. H. MITCHELL GAS DRIERS 5Sheets-Sheet 3 Filed Dec. 5. 1960 FIG. 5

, Inventor LEONARD G.H. MITCHELL W%- A ttorney July 9, 1963 G. H.MITCHELL GAS DRIERS 5 SheetsSheet 4 Filed Dec. 5, 1960 vm mN AttorneyJuly 9, 1963 G. H. MITCHELL GAS DRIERS 5 Sheets-Sheet 5 Filed Dec. 5.1960 E @k R QmE:

Inventor LEONARD G. H. MITCHELL by: AQMVA Aftorne y United States Patent01 3,096,972 GAS DRIERS Leonard G. H. Mitchell, Toronto, Ontario,Canada, assignor to General Steel Wares Limited, Toronto, Ontario,Canada Filed Dec. 5, 1960, Ser. No. 73,619 Claims. (Cl. 263-33) Thisinvention relates to clothes driers and more particularly to a gas firedclothes drier.

The principal object of the invention is to provlde a gas fired clothesdrier which will be extremely 'efficient and extremely safe inoperation.

In particular, it is an important object to provide for an almostinstantaneous detection of a change in normal flame pattern indicatingimproper drier operation and to provide for burner shut-off the instantthat the abnormal flame pattern is detected to eliminate fire hazard.

Another important object is to further provide for an almostinstantaneous detection of an abnormal temperature rise within the drierdrum and to shut off the burner before damage to the clothing can occur.

Still another object is to provide a drier as aforesaid, the cabinet ofwhich will remain cool even directly above the flame area.

Because of the problem of lint gathering at various parts of a clothesdrier, particularly if the lint filter is not frequently cleaned, andbecause of the nature of the clothing itself, particularly clothingwhich may be highly inflammable, it has been considered necessary toremove the open gas flame to a point a substantial distance from theinlet to the drier drum. This conventional arrangement has meant thatthe drying air which is caused to pass through the drum must be led asubstantially distance before entering the drum. As a result,considerable cooling of the air takes place as heat is given up to thewalls of the conducting channel impairing the efliciency of the drier.

According to the present invention there is provided a novel folded airpath arrangement leading into the drum, and the drying air that passesthrough the drum comprises high temperature air that passes through andis directly heated by the flame and enters the drum through the foldedpath, and a volume of air that bypasses but is indirectly heated by theflame, the arrangement being such that although a large volume of dryingair is delivered into the drum the flame is enabled to be brought closeto the drum entrance without danger of the flame being pulled out toenter the drum and ignite clothing or lint deposits in the drum.

-A further important feature resides in dividing the indirectly heateddrying air between a first minor volume that flows past and is separatedfrom the flame by a thin heat transfer surface, and a second majorvolume indirectly heated by the flame and the said minor volume, thesaid minor volume acting as a coolant for the heat trans.- fer surfaceas it passes thereover to pick up heat after which it is led to join thedirectly heated air in the folded air path.

In normal drier operation it will be understood that the flame willassume a substantially constant pattern being pulled downstream by theflow of directly heated drying air, and further according to theinvention there is provided a temperature responsive device foreffecting gas cut-off upon any substantial flame pattern deviation.

In this connection according to the invention the temperature responsivedevice is arranged immediately above the aforementioned heat transfersurface and slightly downstream of the gas burner to receive heat fromsaid ice surface and to be contacted by the first minor volume ofindirectly heated drying air passing over the surface.

A further feature resides in providing in connection with the flamepattern detector a further temperature responsive element to effect gascut-01f upon abnormal temperature rise in the drum.

These and other objects and features of the invention will becomeapparent to those skilled in the art from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIGURE 1 is a perspective, exploded view, partly broken away, of a drierembodying the invention, portions of the drier being omitted for sake ofclarity;

FIGURE 2 is a rear elevational view of the drier with the rear wall ofthe casing cut away;

FIGURE 3 is a side elevational view of the drier with a portion of thecasing broken away;

FIGURE 4 is an enlarged exploded perspective view of the housingcomponents defining the air flow path leading into the drum, taken fromthe rear of the machine;

FIGURE 5 is a perspective view of the burner employed in the drier;

FIGURE 6 is an enlarged, fragmentary, vertical sectional viewillustrating the folded air path and the flame pattern detector, lookingfrom the rear of the machine;

FIGURE 7 is a schematic Wiring diagram of the control circuit of thedrier.

Referring first to FIGURES 1 to 3, the drier comprises a rectangularbase frame 1 from which extends an upright post 2 having journalled inthe upper end thereof a shaft 3 on which is rotatably supported a dryingdrum 4 having an end wall formation 5 carrying a journal block 6receiving the shaft 3 and a perforated peripheral wall 7 which may beformed from a punched sheet, screening or other suitable foraminousmaterial. A motor 8 mounted on a spring-loaded bracket 9 drives a fan 10through a belt 11, the belt passing over a large pulley 12 which isfloatingly mounted on a pivoted bracket 13 carrying a shaft 14 passingthrough the pulley. Shaft 14 carries a relatively smaller pulley 15which drives through a belt 16 a relatively larger pulley 17 mounted onthe drum shaft 3, the pulleys 12, 15 and 17 and belt drives 11 and 16forming a reduction drive to the drum.

Tension is maintained on the belt drives 11 and 16 by means of thesprings 18 and 19 respectively.

Surrounding the drum 4 is a housing 20 which is provided adjacent to thetop with an inlet opening 21 defined in a section 2.2 of the housingformed from a suitable high heat-resistant material. Preferably aperforated plate or screen 23 covers the inlet and the inlet is dividedas shown particularly in FIGURE 4 by means of a strip of suitableheat-resistant material 24. Adjacent to the bottom and preferablysubstantially diametrically opposite to the inlet 21, the housing 20 isprovided with outlet openings 25 which are arranged to open into aconduit member 26 which leads to the [fan 10, there being provided asuitable removable lint filter member 27 adapted to be sleeved into andout of the conduit 26.

The operation of the fan 10' is such that it is arranged to draw airthrough the inlet 21 in the drum housing 20 into and across the dryingdrum 4 and out the housing outlets 25 through the lint filter 27, thefiltered air being discharged either through the exhaust 23 at the rearof the machine, FIGURE 2, or the fan may be arranged to exhaust throughthe front of the machine through the exhaust 28, FIGURE 1.

Mounted on top of the section 22 of the drum housing 20 is an innergenerally triangular shaped housing generally designated at 29, as shownin FIGURE 4, which has an inner baflle '30, as shown in FIGURE 6, thatextends upwardly from the housing 20 at one side of the inlet opening'21 and then extends laterally across the opening to terminate centrallyof the width of the imperforate strip 24 extending across the druminlet. The outer wall 31 of the housing 29 defines with the baflie 30, avertical inlet passage 32a, a tapering transverse passage 32b, and avertical passage 32c terminating at the strip 24. In turn, the strip 24and the baflie 3t} define a return path 32d which opens into the drumthrough the casing inlet 21 beneath the baflle 30. Thus the air flowpath 32a to 32b comprises, as seen, a folded air flow path leading intothe drum.

Spaced above the baflie 36 Within the housing 2? is a thin, heattransfer plate 33 which defines with the outer housing wall 31 a by-passair flow path 33a which joins the folded air flow path at a point abovethe strip 24.

Overlying the housing '29 is a similarly shaped and slightly largerhousing 34 which defines with the housing 29 an air flow by-pass 35 thatcompletely surrounds the inner housing 29 and opens into the drum 4through the housing inlet 21 at the side of the strip 24 opposite tothat through which the air flowing in the folded air path 32a to 3212enters.

Air flowing in the paths 32a to 32d, 33a and 35, is heated by means of agas burner designated at 36 in FIG- URE which projects into the innerhousing 29 through a suitable opening 37, the burner extending in adirection parallel to the drum axis through the vertical portion 32a ofthe folded air flow path.

As seen in FIGURE 4, the inner housing 29 is provided with dependingbent-out lugs 38 which are adapted to enter punched up retaining bosses3 9 in the housing section 22, and the housing section 22 is providedwith upstanding perforated ears 40- adapted to register withcorresponding openings 41 in the outer housing '34 for the reception ofsuitable fasteners, and the gas burner 36 is provided with a suitablemounting bracket 42 for attachment to the housing 29.

With reference to FIGURES 2 and 7, gas is arranged to enter the drierthrough an inlet manually controlled cock 43', FIGURE 2, and isdelivered through suitable solenoid controlled valves generallydesignated at 44, through a gas line 46 to the pilot 72, FIGURE 7, andthrough the main gas line 45 to the burner 36, the control and sequenceof gas flow operation being more fully explained inconnection withFIGURE 7.

The drier drum and its surrounding housing 20 and the housings 29 and Mdefining the air inlet flow path arrangement and the motor and blowerand other components are all contained within a suitable casing 48, andto provide for the introduction and removal of the clothing, thedrum 4,housing 20, and casing 48, are arranged to define a circular entrance4-9 leading into the drum and closed bya suitable door 50.

In the drying of clothes, it is usually desirable to provide a timer,generally designated at 51 in FIGURE 7, to select the time of operationof the drier, and an adjustable thermostat 52 to select the temperatureat which the drier is to operate, the adjustable thermostat being set toturn the source of heat for the drying air on and off as the temperaturewithin the drum reaches a pre-selected low temperature and hightemperature point respectively. As in the usual case, the drier isprovided with a temperature responsive element 53 arranged on thehousing 20 to respond to abnormal temperatures in the drum and shutoffthe heat energy source. According to the present invention, however,there is provided in addition a flame pattern detector 54 whichcomprises a temperature responsive device mounted in a well 5 in theouter housing 34 and projecting through an opening 56 in the innerhousing 29, so that its temperature responsive element lies immediatelyabove the heat transfer plate 33 and slightly downstream with respect tothe burner 66.

When the burner 36 is operating, the primary air for supporting thecombustion of the gas escaping through the series of gas ports 57 isprovided through the dampered controlled primary air inlets 58 at therear of the burner, as shown particularly FIGURE 5, and the air flowingthrough the air passages 32a and 3212 will provide the necessarysecondary air to afford complete combustion of the gas and as well, aquantity of drying air which passes through and is directly heated bythe flame on its way through the folded air flow path into the drum toeflect a draw-out of the flame to give the flame pattern 59 as show ninsolid lines in FIGURE 6. It will be noted that the burner and flame aredisplaced from the inlet 21 to the drum around a bend in the foldedairpath as defined by the free end of the inner baflle 30.

In addition to the directly heated drying air that passes through theflame, it will be understood that there will be a small Volume ofindirectly heated air flowing over the heat transfer plate 33 landthrough the flow path 33a to rejoin the directly heated drying air inthe latter portion of the folded air path. The air flowingin the path33awill pick up the heat from the heat transfer plate 33 and in so doingwill serve as a coolant for the flame pattern detector 54. The dryingair passing directly through the flame 59 will, of course, be thehighest temperature air entering the drum, but the air flowing throughthe path 3311 will also be relatively high temperature air. In addition,air will be drawn into the drum through the air flow path 35 surroundingthe inner housing '29. This air will be heated indirectly by the flameand by the air flowing through the path 33a and will be maintainedseparate from the directly heated air flowing through the folded airpath. The air flow through the path 35- 'will serve as a further coolantto the flame pattern detector and will also act as an insulating barrierto the transfer of heat directly up to the main casing 48 so that thedrier will be cool on the outside. Further by having a portion of thedrying air by-passing the flame, the drawout of the flame will beminimized and by the provision of this by-pass arrangement, coupled withthe folded air path for the directly heated drying air, the flame can bebrought relatively close to the entrance of the drum so that the heat ofthe drying air is not dissipated in the drier casing and air flow pathbefore entering the drum. While the air entering the drum through thepath 35 will not be at the same high temperature [as the directly heatedair, it will nevertheless have appreciable drying capacity and will havesubstantial volume flow.

As will be seen from FIGURE 6, should there be any deviation in thepattern of the flame 59, such as to reduce its pull-out, the flame willmove to provide a flame pattern and occupy the dotted position shown at60. This will bring the flame substantially immediately under the flamepattern detector 54 which is arranged to open circuit the controlcircuit of FIGURE 7 upon detecting any abnormal temperature rise.

It will be appreciated that any one of a number of conditions whichwould give rise to dangerous drier operation will effect the shift ofthe flame pattern from the solid line showing of '59 to the dotted lineshowing of 60. For example, if the fan should fail to operate, or if thelint filter becomes plugged, the air flow through the drier will bestopped or reduced and immediately the flame will move back to contactthe heat transfer plate substantially beneath the flame patterndetector. Further, the reduced air flow will reduce the flow of coolingair through the passage 3302, so that not only is there the applicationof the flame almost directly onto the flame pattern detector, but thecoolant for the flame pattern detector is reduced or removed. As aresult, it has been found that the flame pattern detector respondsalmost instantaneously to flame pattern changes reducing flame pull-out,and as explained in further detail in connection with FIGURE 7, theoperation of the flame pattern detector is to cut off gas flow.

With reference to FIGURE 7, the electrical control circuit is fed fromthe line through a suitable plug-in connector 61 which delivers currentto the timer 51 comprised by the timer motor 62 and the timer controlmechanism 63 for setting the time of drying, and to the main motor 8 fordriving the drum in rotation. Preferably, the circuit is provided with acircuit breaker 64 and a door switch 65 which, with the door closed,occupies the solid line position shown to energize the control circuit.When the door is open, switch 65 will occupy the dotted line position toapply voltage to a lamp 66 which is arranged to shine into the interiorof the drum 4 for lighting purposes. Current to the solenoids of thevalves 44 is delivered through the temperature responsive element '53and the flame pattern detector 54 arranged in series with the devices 53and 54 being of the type having normally closed contacts until subjectedto temperatures above desired pre-selected temperature limits.

From the flame pattern detector 54, current is delivered to a warpswitch 67 which is adapted to remain closed While subjected to the heatfrom a heater 68' for a given period, but upon heat being continued tobe directed at the switch, the switch is adapted to open and remain openfor a given period.

From the warp switch 67, current is delivered through its normallyclosed contacts to a transformer 69 which is arranged to energize a glowcoil 70. In addition current flow is delivered through the normallyclosed contacts of the warp switch to the pilot valve solenoid 71 toopen the valve and provide gas flow to the pilot 72. A further currentpath in series with the closed contacts of the warp switch leads throughthe adjustable thermostat 52 and solenoid 73 for opening the main gasvalve, but this circuit remains open with respect to the return line 74-through the hot con-tact H of the pilot detector plug-in unit 75 whichincorporates a switch contact 76 movable from a position to which it isurged to return in contact with the cold contact C to a positioncontacting the hot contact H. As will be seen, with the switch contact76 occupying its normal position in contact with the contact C, thetransformer 69 is connected to a return line 74 returning to theconnector 61.

The pilot 72, when lit, is arranged to heat an expanding material, suchas mercury, in a tube 77, and when expanded, the mercury is adapted tooperate a plunger 78 to actuate the switch contact 76 to break itsconnection with contact C and to make connection with the contact H toenergize the main gas flow solenoid 73 to allow gas flow to the burner36.

Thus, when the drier is first turned on, current flow is deliveredthrough the closed contacts of the wrap switch 67 to the transformer 69which is coupled to the return circuit through the switch contact 76 incontact with the cold contact C of the plug-in unit 75. This connectionlights the glow coil 70. At the same time, the circuit is made throughthe pilot valve solenoid 71 to turn on the gas to the pilot 72 and thisgas will be ignited by the glow coil 70.

As soon as the mercury in the tube 77 is heated so that the plunger 7 8is actuated to move switch contact 76 from the cold contact C to the hotcontact H, the main solenoid 73 will be energized to open the main valveand allow gas into the burner where it will be ignited.

When the switch contact 76 is operated to move it from contact with thecold contact C to the hot contact H, the pilot solenoid 71 will remainenergized and the pilot will remain on, but the transformer 69 and theheater 68 will be de-energized saving burning out of the glow coil andpreventing suflicient heat build up on the contacts of the warp switch67 to open the switch.

It will be appreciated that should either of the temperature responsiveelement 53 or flame pattern detector 54 open circuit due to abnormaltemperature rises, current to the warp switch 67 will be interruptedcutting off current flow to the heater 68, transformer 69 and solenoids71 and 73, de-energizing the glow coil and closing the gas valves to cutoff gas flow to the pilot and burner.

The adjustable thermostat 52 is arranged in series with the main gasvalve solenoid 73 so that as it cuts on and off as it reaches itstemperature limits, gas flow to the burner will be cut on and off, butthe pilot will continue to operate.

Should gas flow not reach the pilot 72 for any reason whatsoever, theswitch contact 76 of the plug-in unit 75 will remain closed againstcontact C and heater 68 will be continued to be energized through thiscontact which connects back to the return line 74 and the glow coil willbe continued to be energized. It will be understood that in due coursethe heat trom the heater 68 will build up sufficiently to open thecontacts of the warp switch 67 dc-energizing the entire circuit untilthe warp switch becomes re-set as for instance by a lapse of time.

To avoid variations in the flame pattern due to changes in pressure inthe gas source, there is preferably provided a suitable pressureregulator 79 maintaining uniform gas pressure to the burner 36.

It will be understood that a drier as described will operate safely withpositive controls to ensure gas shut off upon any abnormal conditionbeing set up in the drier, and at the same time, when operating, therewill be a substantial flow of both high temperature directly heat dryingair and lower temperature indirectly heated air to provide a rapid rateof drying. Further, it will be seen that through the use of the outercasing 34, substantially all heat will be retained and delivered intothe drier allowing the drier to remain cool on the outside andaugmenting the drying capacity from a given heat source.

While the preferred embodiment of the invention has been illustrated anddescribed, it Will be understood that variations in details and thearrangement of parts and other modifications as may be apparent to thoseskilled in the art may be made without departing from the spirit of theinvention or scope of the appended claims.

What I claim is:

1. In a gas drier of the type comprising a perforated drum rotatablymounted in a housing having an inlet for heated drying air, and anoutlet for moisture laden air and positive air circulating means forcausing air to enter said drum through said housing inlet and exhaustfrom said drum through said housing outlet, means defining a folded airpath leading into said housing inlet, gas burner means for producing anopen flame in said folded air path and separated from said housing inletby a reverse fold in said path requiring air passing through said flameto reverse flow direction through substantially in said flow path toreach said housing inlet, means dividing air flow into said housinginlet into directly heated drying air passing through said flame andindirectly heated drying air heated by but bypassing said flame, meansto divide said indirectly heated drying air between a first minor airflow stream separated from the open burner flame by a thin heat transferwall and a second major air flow stream isolated from the "burner flameby said minor secondary air flow stream, and a flame pattern detectorlocated dovmstream of said gas burner in said folded air path anddisposed and arranged to cut oil gas flow upon appreciable flame patternchange, said flame pattern detector comp-rising a thermal responsivedevice disposed substantially in contact with said heat transfer walland exposed to said minor air flow stream of indirectly heated air.

2. A gas drier as claimed in claim 1 in which said thermal responsivedevice is disposed above and slightly downstream towards the housinginlet with respect to said burner.

3. A gas drier as claimed in claim 1 in which gas flow to said burner iscontrolled by a solenoid operated valve and said thermal responsivedevice is connected to control the solenoid of said valve to shut offgas flow to said burner upon abnormal temperature rise in said thermalresponsive device.

4. A gas drier as claimed in claim 3 in which said burner is a pilotoperated burner and gas flow to the pilot of said burner is controlledby a solenoid operated valve and said thermal responsive device isconnected to control the solenoid of said latter valve to shut off pilotgas flow upon abnormal temperature rise in said thermal responsivedevice.

5. In a gas drier, a rotatable drum, means defining a fielded air flowpath presenting a reverse fold and leading into said drum, burner meansproducing a flame for heating air flowing in said folded air path, meansdefining a flow path encompassing and by-passing said folded air flowpath, and flame pattern detector means responsive to flame patterns insaid folded path for controlling said heating means located in said flowpath encompassing and by-passing said folded air flow path anddownstream of said heating means.

References Cited in the file of this patent UNITED STATES PATENTS1,848,150 Becker Mar. 8, 1932 2,194,713 Mitchell Mar. 26, 1940 2,867,430Hull-a1 Jan. 6, 1959 2,919,750 Cobb Jan. 5, 1960 2,931,687 Mitter Apr.5, 1960 2,958,140 Smith NOV. 1, 1960 i FOREIGN PATENTS 133,505 GreatBritain Oct. 16, 1919

1. IN A GAS DRIER OF THE TYPE COMPRISING A PERFORATED DRUM ROTATABLYMOUNTED IN A HOUSING HAVING AN INLET FOR HEATED DRYING AIR, AND ANOUTLET FOR MOISTURE LADEN AIR AND POSITIVE AIR CIRCULATING MEANS FOARCAUSING AIR TO ENTER SAID DRUM THROUGH SAID HOUSING INLET AND EXHAUSTFROM SAID DRUM THROUGH SAID HOUSING OUTLET, MEANS DEFINING A FOLDED AIRPATH LEADING INTO SAID HOUSING INLET, GAS BURNER MEANS FOR PRODUCING ANOPEN FLAME IN SAID FOLDED AIR PATH AND SEPARATED FROM SAID HOUSING INLETBY A REVERSE FOLD IN SAID PATH REQUIRING AIR PASSING THROUGH SAID FLAMETO REVERSE FLOW DIRECTION THROUGH SUBSTANTIALLY 180* IN SAID FLOW PATHTO REACH SAID HOUSING INLET, MEANS DIVIDING AIR FLOW INTO SAID HOUSINGINLET INTO DIRECTLY HEATED DRYING AIR PASSING THROUGH SAID FLAME ANDINDIRECTLY HEATED DRYING AIR HEATED BY BUT BYPASSING SAID FLAME, MEANSTO DIVIDE SAID INDIRECTLY HEATED DRYING AIR BETWEEN A FIRST MINOR AIRFLOW STREAM SEPARATED FROM THE OPEN BURNER FLAME BY A THIN HEAT TRANSFERWALL AND A SECOND MAJOR AIR FLOW STREAM ISOLATED FROM THE BURNER FLAMEBY SAID MINOR SECONDARY AIR FLOW STREAM, AND A FLAME PATTERN DETECTORLOCATED DOWNSTREAM OF SAID GAS BURNER IN SAID FOLDED AIR PATH ANDDISPOSED AND ARRANGED TO CUT OFF GAS FLOW UPON APPRECIABLE FLAME PATTERNCHANGE, SAID FLAME PATTERN DETECTOR COMPRISING A THERMAL RESPONSIVEDEVICE DISPOSED SUBSTANTIALLY IN CONTACT WITH SAID HEAT TRANSFER WALLAND EXPOSED TO SAID MINOR AIR FLOW STREAM OF INDIRECTLY HEATED AIR.